docs(legibility): add 18 per-domain README.md files (DOC-6)

Backend (9): document, person, tag, user, geschichte, notification,
ocr, audit, dashboard.
Frontend (8): document, person, tag, user, geschichte, notification,
ocr, shared.
OCR service (1): ocr-service/README.md.

Each README covers: what the domain owns, explicit non-ownership,
public surface (verified by grep against the codebase), internal
layout, and cross-domain dependencies.

Closes #400
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/ocr/README.md

@@ -0,0 +1,27 @@
+# ocr (frontend)
+
+UI for OCR job management, progress display, and sender-model training in the admin/enrichment panel.
+
+## What this domain owns
+
+Components: `OcrProgress.svelte`, `OcrTrigger.svelte`, `OcrTrainingCard.svelte`, `SegmentationTrainingCard.svelte`, `TrainingHistory.svelte`.
+Utilities: `translateOcrProgress.ts` (progress-state → display-string mapping), `training.ts` (training API helpers).
+
+## What this domain does NOT own
+
+- OCR processing — all text recognition runs in the Python `ocr-service/` container. The frontend shows job state; it does not run OCR.
+- Transcription block display — rendered by `document/transcription/` components.
+
+## Key components
+
+| Component                         | Used in                       | Notes                                                    |
+| --------------------------------- | ----------------------------- | -------------------------------------------------------- |
+| `OcrProgress.svelte`              | document header, enrich panel | Progress bar and status label for an active OCR job      |
+| `OcrTrigger.svelte`               | enrich panel, document detail | Button to start an OCR job; disabled when one is running |
+| `OcrTrainingCard.svelte`          | `/admin/ocr`                  | Trigger sender-model training; shows training history    |
+| `SegmentationTrainingCard.svelte` | `/admin/ocr`                  | Trigger segmentation training                            |
+| `TrainingHistory.svelte`          | `/admin/ocr`                  | List of past training runs with status                   |
+
+## Backend counterpart
+
+`backend/src/main/java/org/raddatz/familienarchiv/ocr/README.md`